Study On Residual Strength Assessment And Maintenance Strategy For Oil And Gas Pipelines With Defects

Due to the oil and gas with high pressure, flammable, explosive, coupled with onshore oil and gas pipelines conveying long distance, across geographical complex type, and with the oil and gas pipeline service time of growth, the possibility of failure also increases, if the pipeline failure accident occured, it will cause significant casualties and property losses, also pose a great threat to the environment. To carry out the defective pipeline corrosion and cracking of residual strength evaluation and establish reasonable maintenance strategy, it has the important significance to furthest ensure oil and gas pipeline running safely and efficiently, and also has been the research focus in this field.On the basis of analysis pipeline risk assessment model and residual strength evaluation method and its advantages and disadvantages, with fracture mechanics analysis method as the foundation, for the oil and gas pipeline in uniform corrosion and local corrosion defects,residual strength evaluation was established to determine pipe risk acceptability and whether the safe operation, so that the reasonable maintenance plan for the pipeline was constituted, or further evaluation was needed by adjusting the related parameters. Then for the axial inside and outside surface crack, net section under axial force of bending moment ring to the inside and outside surface crack, and the net cross section under internal pressure and the axial force of semi elliptical ring to the inside and outside surface crack, crack pipe residual strength evaluation model was set up respectively, to calculate toughness ratio and the load ratio, and analysis the section risk acceptable level with the failure assessment diagram as the theory basis. Based on the primary residual strength evaluation model, the complete residual strength evaluation software system was developed by using C# language. Finally, based on the theory of random process and Markov, introducing the repair rate and cost, the decision model of oil and gas pipeline maintenance was established, to obtain availability and total cost of pipeline under different maintenance strategies.Because the research level is limited, the model established in this paper need to collect more sufficient information, also there are still some deficiencies in the model’s correctness and completeness, and further research is needed.